1. Field of the Invention: The present invention relates to an apparatus for producing hooks on loop-and-hook fasteners with an ultrasonically vibratable cutter.
2. Description of the Prior Art:
Known apparatus for producing hooks on loop-and-hook fasteners include a cutter vibratable under ultrasonic energy and a fixed cutter for jointly guiding loops to be cut off from a loop tape. The known apparatus is disadvantageous in that the ultrasonically vibratable cutter tends to contact portions of loops which should not be cut off, thus severing or otherwise damaging such loop portions. When the ultrasonically vibratable cutter happens to engage both legs of a loop, the legs are completely cut off from the loop tape. To prevent such undesirable cutting of loops, the ultrasonically vibratable cutter should be kept out of contact with the loops, which then could not be raised and guided properly and hence would be cut off at different heights. Another problem with the prior apparatus is that loop tapes or sheets with loops interknitted or interwoven therein should be fabricated with great care for dimensional accuracy and the apparatus should be operated under strict control to protect loop legs from unwanted severance.